Recently, a public line network such as the Internet has allowed terminals to share a screen. In such screen sharing, a sender's terminal transmitting shared screen data is connected with a receiver's terminal receiving shared screen data through a screen sharing server. Then, the screen data of the sender's terminal is displayed on the receiver's terminal.
As disclosed in Patent Document 1, only specific IP addresses are permitted to access the screen sharing server, and then the users are authenticated, so as to allow only specific users to share a screen in such screen sharing.